1. Field of the Invention
In the Oxirane process for the co-production of propylene oxide and styrene monomer, propylene is reacted with ethylbenzene hydroperoxide to form propylene oxide and methyl benzyl alcohol (1-phenyl ethanol), and the methyl benzyl alcohol is dehydrated to styrene. Significant amounts of phenol are formed which, in accordance with the present invention are separated from methyl benzyl alcohol and associated acetophenone by extractive distillation with sulfolane as extractive distillation solvent.
2. Description of the Prior Art
An extremely successful process for the co-production of propylene oxide and styrene monomer involves the molecular oxygen oxidation of ethyl benzene to form ethyl benzene hydroperoxide, the catalytic reaction of the hydroperoxide with propylene to form propylene oxide and 1-phenyl ethanol, and the dehydration of the 1-phenyl ethanol to styrene monomer. The basic patent describing this process is U.S. Pat. No. 3,351,635.
There is formed in this process a stream comprised of 1-phenyl ethanol and acetophenone which also contains substantial amounts of phenol. It is important from the standpoint of product purity and yield that the phenol be removed.
Phenol separation can be accomplished by caustic treatment but this results in the formation of spent caustic waste streams which pose increasingly difficult problems of disposal. U.S. Pat. No. 5,171,868 provides a process whereby the amount of spent caustic to be disposed of can be substantially reduced. However, further improvements would be advantageous. Because of the close-boiling nature of the components, it is not economical to separate a mixture comprised of 1-phenyl ethanol, acetophenone and phenol by conventional distillation procedures.